The experimental Hematology Section of the Clinical Oncology Program, Division of Cancer Treatment, National Cancer Institute, maintains a serum repository in which are stored samples collected from patients of the DCT at the time of their admission and at subsequent times during their hospital course. This repository contains 30,000 entries and is used for retrospective analyses of patients' sera enrolled in all of the treatment programs. This computerized serum repository is a resource being used for clinical investigation by a large number of investigators to clarify issues of antibiotic support, Burkitt's Lymphoma, and the development of an in vitro assay for cardidasis.